(a) Technical Field of the Invention
The present invention relates to a clutch that enhances engaging power, and in particular to a clutch of high engaging power and featuring stable engagement, which increases the engaging power of each clutch shoe to smoothen and stabilize power transmission.
(b) Description of the Prior Art
A centrifugal clutch is widely used in an automatic transmission mechanism of a motorcycle. The centrifugal clutch functions to reflect the rotational speed of a driven pulley to cause clutch weights that are in pivotal connection with a base to expand the clutch weights, in response to the increasing of rotational speed, for causing the wear pads to engage a rim of a driven disk and thus transmitting power to a driven shaft for driving wheels of motorcycles forward. When the rotational speed is reduced, the clutch weights are moved inward and closed to each other, and the transmission of power to the driven shaft is cut off. To allow the clutch weights to reflect the variation of rotational speed and to induce effective engagement, each clutch weight is provided with tension spring (return element) on opposite sides of the pivotal point and connecting between adjacent clutch weights. Timing of expansion/closing of the clutch weights is determined by the tension of the spring.
Theoretically, every two adjacent clutch weights are constrained by the inter-connecting spring. The response characteristics of each clutch weight in action and angle of expansion/closing operation due to outward movement caused by rotation can be made the identical if the tension of all the springs are the same. However, in practice, the base is often in a non-constant speed rotation due to the fact that the rotational speed of the driven pulley is subject to variation by different operations of the acceleration pedal in response to different driving conditions. This makes the centrifugal force of each clutch weight exhibiting difference in response timing. Thus, during the outward expansion and inward closing process, the clutch weight is subject to unstable expansion, leading to oscillatory phenomena of engaging, which causes the transmission of power unstable.